Method for the preparation of sulfinpyrazone

ABSTRACT

The present disclosure discloses a method for the preparation of sulfinpyrazone, which is produced in two steps with a total yield of 48%, wherein thiophenol as the starting material is electrocatalytically coupled with dichloroethane to obtain 2-chloroethyl phenyl sulfoxide, which then undergoes a substitution reaction with 1,2-diphenyl-3,5-pyrazolidinedione to produce sulfinpyrazone. Compared with the prior art, the present method is characterized by high yield, short steps, less three wastes, good chemical selectivity, no need to use strong bases and oxidants, safe and simple operation, and easy to realize industrial production.

TECHNICAL FIELD

The present disclosure relates to the field of drug synthesis, and in particular to a method for the preparation of sulfinpyrazone.

BACKGROUND

The structure of sulfinpyrazone is shown in formula I.

Sulfinpyrazone, a derivative of phenylbutazone, has the effect of inhibiting platelet aggregation and release in vivo, and can reversibly inhibit platelet prostaglandin synthetase. Sulfinpyrazone can competitively inhibit the active reabsorption of urate at the proximal tubule, increase uric acid excretion, reduce the concentration of uric acid in the blood, and slow or prevent the formation of gouty nodules and articular gouty lesions. It can also inhibit platelet aggregation and increase platelet survival time. It also has a weak anti-inflammatory and analgesic effect.

In the literature Volumen XLIV, Fasciculus 11961, 28, 233. and Chin. J. Pharm., 1999, 30, 100. reported that sulfinpyrazone was synthesized as follows: thiophenol as raw material was reacted with 1,2-dichloroethane, then undergone a nucleophilic substitution reaction with diethyl malonate, followed by a transesterification with diphenylhydrazine, and finally thioether was oxidized to sulfoxide to obtain sulfinpyrazone.

The above two routes have long and tedious steps with low yield. In addition, more importantly, in the last step, thioether is easily over-oxidized to sulfone by the hydrogen peroxide and acetic acid system, so that it is difficult to control the product to remain on the step of obtaining sulfoxide.

In view of the above, since the synthesis route in the prior art not only has long steps and low yield, but also has difficulties in controlling the product retention, there is an urgent need for a green, easy-to-operate, efficient and fast method to replace the method in the prior art for the preparation of sulfinpyrazone.

SUMMARY

The present disclosure provides a method for the preparation of sulfinpyrazone. For the first time, the present disclosure uses thiophenol as raw material and produces sulfinpyrazone through two steps of electrocatalytic oxidation and nucleophilic substitution. This method has a short step, is green, has high purity and stable quality, does not use hydrogen peroxide as an oxidant, and overcomes the disadvantage of easily overoxidizing thioether to sulfone in the classical method of the prior art.

The purpose of the present disclosure is to provide a method for the preparation of sulfinpyrazone in order to solve the above-mentioned problems in the prior art.

In order to achieve the above purpose, the following technical solutions are used in the present disclosure.

A method for the preparation of sulfinpyrazone with the following synthetic routes:

wherein electrolyte represents an electrolyte, current represents a current, temperature represents a temperature, salt represents a salt, base represents a base, additive represents an additive, and solvent represents a solvent.

As a further improvement of this solution, it specifically includes the following steps of:

-   (1) dissolving thiophenol as shown in formula 3 and electrolyte in a     mixed solution of 1,2-dichloroethane and water and reacting by     passing the current for 1 to 48 hours to obtain 2-chloroethyl phenyl     sulfoxide as shown in formula 2; and -   (2) mixing and dissolving 2-chloroethyl phenyl sulfoxide as shown in     formula 2, 1,2-diphenyl-3,5-pyrazolidinedione as shown in formula 4,     the base and the additive in the solvent, and reacting by heating     under nitrogen atmosphere for 1 to 48 hours, and after completing     the reaction, subjecting the reaction mixture to a column     chromatography to obtain sulfinpyrazone as shown in formula 1.

As a further improvement of this solution, the conditions of the electrodes in step (1) are as follows: the anode is selected from one of graphite felt, platinum, and nickel electrodes, the cathode is selected from graphite felt, platinum, nickel, and carbon sheet electrodes, and the electrode specifications are both 1 cm×1 cm.

As a further improvement of this solution, the electrolyte in step (1) is any one of tetrabutylammonium bromide, tetrabutylammonium tetrafluoroborate, tetra-n-octylammonium bromide, tetrabutylammonium hexafluorophosphate, lithium perchlorate, ammonium perchlorate, and tetrabutylammonium iodide, and the amount of electrolyte is 0.5-2 times that of thiophenol.

As a further improvement of this solution, the water in step (1) is any one of distilled water and deionized water, and the amount thereof is 0.5-10 times that of thiophenol.

As a further improvement of this solution, the current in step (1) is 4-30 mA.

As a further improvement of this solution, the temperature in step (1) is 30-70° C.; and the amount of 1,2-dichloroethane in step (1) by volume is 5-30 times that of compound 3.

As a further improvement of this solution, the solvent in step (2) is selected from any one or more of acetone, acetonitrile, and n-hexane.

As a further improvement of this solution, the base in step (2) is selected from any one of cesium carbonate, sodium hydroxide, potassium hydroxide, sodium ethoxide, potassium ethoxide, triethylamine, and diisopropylethylamine; the additive is selected from any one of sodium iodide, potassium iodide, lithium iodide, and ammonium iodide; and the reaction temperature in step (2) is 50-70° C.

As a further improvement of this solution, the amount of the compound 1,2-diphenyl-3,5-pyrazolidinedione in step (2) is 1.0-4.0 times that of 2-chloroethyl phenyl sulfoxide; the amount of base is 1.0-4.0 times that of 2-chloroethyl phenyl sulfoxide; the amount of additive is 1-5 times that of 2-chloroethyl phenyl sulfoxide; and the amount of solvent is 5-10 times that of 2-chloroethyl phenyl sulfoxide.

Compared with the prior art, the present disclosure has the following beneficial effects:

-   a) introducing a green and environmentally friendly electrochemical     method into the synthesis steps, greatly shortening the reaction     steps and increasing the overall yield; -   b) avoiding the use of strong bases and hydrogen peroxide as an     oxidant, improving the atomic economy and reducing environmental     pollution; and -   c) fundamentally overcoming the problem of easy over-oxidation of     chloroethyl sulfide to chloroethyl sulfone under the hydrogen     peroxide system, and improving the selectivity of the reaction. The     present method has good application value and potential     socio-economic benefits.

DETAILED DESCRIPTION

In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the following further description of the present disclosure in conjunction with the examples:

A method for the preparation of sulfinpyrazone with the following synthetic routes:

It specifically includes the following steps of:

-   (1) dissolving thiophenol as shown in formula 3 and electrolyte in a     mixed solution of 1,2-dichloroethane and water and reacting by     passing a current for 1 to 48 hours to obtain 2-chloroethyl phenyl     sulfoxide as shown in formula 2; and -   (2) mixing and dissolving 2-chloroethyl phenyl sulfoxide as shown in     formula 2, 1,2-diphenyl-3,5-pyrazolidinedione as shown in formula 4,     a base and an additive in a solvent, and reacting by heating under     nitrogen atmosphere for 1 to 48 hours, and after completing the     reaction, subjecting the reaction mixture to a column chromatography     to obtain sulfinpyrazone as shown in formula 1.

Among which, the conditions of the electrodes in step (1) are as follows: the anode is selected from one of graphite felt, platinum, and nickel electrodes, the cathode is selected from graphite felt, platinum, nickel, and carbon sheet electrodes, and the electrode specifications are both 1 cm×1 cm; the electrolyte in step (1) is any one of tetrabutylammonium bromide, tetrabutylammonium tetrafluoroborate, tetra-n-octylammonium bromide, tetrabutylammonium hexafluorophosphate, lithium perchlorate, ammonium perchlorate, and tetrabutylammonium iodide, and the amount of electrolyte is 0.5-2 times that of thiophenol; the water in step (1) is any one of distilled water and deionized water, and the amount thereof is 0.5-10 times that of thiophenol; the current in step (1) is 4-30 mA; the temperature in step (1) is 30-70° C.; and the amount of 1,2-dichloroethane in step (1) by volume is 5-30 times that of compound 3.

Among which, the solvent in step (2) is selected from any one or more of acetone, acetonitrile, and n-hexane; the base in step (2) is selected from any one of cesium carbonate, sodium hydroxide, potassium hydroxide, sodium ethoxide, potassium ethoxide, triethylamine, and diisopropylethylamine; the additive is selected from any one of sodium iodide, potassium iodide, lithium iodide, and ammonium iodide; the reaction temperature in step (2) is 50-70° C.; the amount of the compound 1,2-diphenyl-3,5-pyrazolidinedione in step (2) is 1.0-4.0 times that of 2-chloroethyl phenyl sulfoxide; the amount of base is 1.0-4.0 times that of 2-chloroethyl phenyl sulfoxide; the amount of additive is 1-5 times that of 2-chloroethyl phenyl sulfoxide; and the amount of solvent is 5-10 times that of 2-chloroethyl phenyl sulfoxide.

Example 1

2-Chloroethyl phenyl sulfoxide 2 was prepared as follows:

The reaction flask was sequentially added with thiophenol 3 (220.0 mg, 2.0 mmol), tetrabutylammonium tetrafluoroborate (330.0 mg, 1.0 mmol), water (180.0 uL, 10.0 mmol) and 1,2-dichloroethane (4.0 mL), and capped with a rubber stopper with 2 electrodes inserted, a graphite felt anode and a platinum sheet cathode, respectively. The system was reacted for 16 hours at a constant current of 20 mA. After completing the reaction, the solvent was removed by distillation under reduced pressure, and the residue was separated by column chromatography on silica gel with petroleum ether:ethyl acetate=5:1 as an eluent to successfully obtain 312.0 mg of 2-chloroethyl phenyl sulfoxide 2 as a colorless transparent oily liquid in 83% yield.

NMR characterization of 2-chloroethyl phenyl sulfoxide 2:

-   NMR (400 MHz, CDCl₃) δ 7.61 (dd, 1=7.6, 2.0 Hz, 2H), 7.54-7.49 (m,     3H), 4.97-3.90 (m, 1H), 3.65-3.59 (m, 1H), 3.16-3.12 (m, 2H). 13C     NMR (100 MHz, CDCl₃) δ 142.6, 131.3, 129.4, 123.7, 59.2, 36.6. HRMS     (ESI): calcd for C₈H₁₀ClOS [M+H]′ 189.0135, found 189.0126.

Example 2

2-Chloroethyl phenyl sulfoxide 2 was prepared as follows:

The reaction flask was sequentially added with thiophenol 3 (20.0 mg, 2.0 mmol), tetrabutylammonium tetrafluoroborate (660.0 mg, 2.0 mmol), water (180.0 uL, 10.0 mmol) and 1,2-dichloroethane(4.0 mL), and capped with a rubber stopper with 2 electrodes inserted, a graphite felt anode and a platinum sheet cathode, respectively. The system was reacted for 16 hours at a constant current of 20 mA. After completing the reaction, the solvent was removed by distillation under reduced pressure, and the residue was separated by column chromatography on silica gel with petroleum ether: ethyl acetate=5:1 as an eluent to successfully obtain 285.7 mg of 2-chloroethyl phenyl sulfoxide 2 as a colorless transparent oily liquid in 76% yield.

Example 3

2-Chloroethyl phenyl sulfoxide 2 was prepared as follows:

The reaction flask was sequentially added with thiophenol 3 (220.0 mg, 2.0 mmol), tetrabutylammonium bromide (332.0 mg, 1.0 mmol), water (180.0 uL, 10.0 mmol) and 1,2-dichloroethane (4.0 mL), and capped with a rubber stopper with 2 electrodes inserted, a graphite felt anode and a platinum sheet cathode, respectively. The system was reacted for 16 hours at a constant current of 20 mA. After completing the reaction, the solvent was removed by distillation under reduced pressure, and the residue was separated by column chromatography on silica gel with petroleum ether: ethyl acetate=5:1 as an eluent to successfully obtain 203.0 mg of 2-chloroethyl phenyl sulfoxide 2 as a colorless transparent oily liquid in 54% yield.

Example 4

2-Chloroethyl phenyl sulfoxide 2 was prepared as follows:

The reaction flask was sequentially added with thiophenol 3 (220.0 mg, 2.0 mmol), tetrabutylammonium tetrafluoroborate (330.0 mg, 1.0 mmol), water (180.0 uL, 10.0 mmol) and 1,2-dichloroethane (4.0 mL), and capped with a rubber stopper with 2 electrodes inserted, a graphite felt anode and a platinum sheet cathode, respectively. The system was reacted for 16 hours at a constant current of 10 mA. After completing the reaction, the solvent was removed by distillation under reduced pressure, and the residue was separated by column chromatography on silica gel with petroleum ether: ethyl acetate=5:1 as an eluent to successfully obtain 229.3 mg of 2-chloroethyl phenyl sulfoxide 2 as a colorless transparent oily liquid in 61% yield.

Sulfinpyrazone 1 in step 2) was prepared as shown in Examples 5 to 9:

Example 5

The reaction flask was sequentially added with 2-chloroethyl phenyl sulfoxide 2 (189.0 mg, 1.0 mmol), 1,2-diphenyl-3,5-pyrazolidinedione 4 (378.2 mg, 1.5 mmol), cesium carbonate (488.7 mg, 1.5 mmol), sodium iodide (149.9 mg, 1.0 mmol), and acetone (6 mL), wherein the three-necked flask was inserted with a condenser tube connected with a three-way valve with a balloon on one side and covered with a rubber stopper on the other side for the replacement of nitrogen. The mixture was refluxed at 65° C. for 12 hours. At the end of the reaction, acetone was removed by distillation under reduced pressure, and then the residue was dissolved by adding an appropriate amount of water. The pH of the solution was adjusted to 5-6 by adding 10% dilute hydrochloric acid, and the solution was extracted by adding ethyl acetate (10 mL×3). The organic layer was combined and dried with anhydrous sodium sulfate, and the organic solvent was removed by distillation under reduced pressure. The residue was separated by column chromatography on silica gel with dichloromethane:ethyl acetate=10:1 as an eluent to successfully obtain 234.6 mg of sulfinpyrazone 1 as a white solid in 58% yield.

NMR characterization of sulfinpyrazone 1:

-   ¹H NMR (400 MHz, CDCl₃) δ 7.61 (dd, J=7.6, 1.6 Hz, 2H), 7.52-7.47     (m, 3H), 7.31-7.24 (m, 9H), 7.16 (t, J=6.8 Hz, 2H), 3.52 (t, J=7.4     Hz, 1H), 3.33-3.26 (m, 1H), 3.09-3.02 (m, 1H), 2.55-2.45 (m, 1H),     2.23-2.20 (in, 1H). 13C NMR (100 MHz, CDCl₃) δ 168.8, 142.7, 135.2,     131.1, 129.3, 129.0, 127.0, 124.0, 122.6, 52.2, 44.1, 20.7. HRMS     (ESI): calcd for C₂₃H₂₁N₂O₃S [M+H]⁺ 405.1267, found 405.1261.

Example 6

The reaction flask was sequentially added with 2-chloroethyl phenyl sulfoxide 2 (189.0 mg, 1.0 mmol), 1,2-diphenyl-3,5-pyrazolidinedione 4 (302.6 mg, 1.2 mmol), cesium carbonate (391.0 mg, 1.2 mmol), sodium iodide (149.9 mg, 1.0 mmol), and acetone (6 mL), wherein the three-necked flask was inserted with a condenser tube connected with a three-way valve with a balloon on one side and covered with a rubber stopper on the other side for the replacement of nitrogen. The mixture was refluxed at 65° C. for 12 hours. At the end of the reaction, acetone was removed by distillation under reduced pressure, and then the residue was dissolved by adding an appropriate amount of water. The pH of the solution was adjusted to 5-6 by adding 10% dilute hydrochloric acid, and the solution was extracted by adding ethyl acetate (10 mL×3). The organic layer was combined and dried with anhydrous sodium sulfate, and the organic solvent was removed by distillation under reduced pressure. The residue was separated by column chromatography on silica gel with dichloromethane:ethyl acetate=10:1 as an eluent to successfully obtain 165.8 mg of sulfinpyrazone 1 as a white solid in 41% yield.

Example 7

The reaction flask was sequentially added with 2-chloroethyl phenyl sulfoxide 2 (189.0 mg, 1.0 mmol), 1,2-diphenyl-3,5-pyrazolidinedione 4 (302.6 mg, 1.2 mmol), cesium carbonate (391.0 mg, 1.2 mmol), sodium iodide (224.8 mg, 1.5 mmol), and acetone (6 mL), wherein the three-necked flask was inserted with a condenser tube connected with a three-way valve with a balloon on one side and covered with a rubber stopper on the other side for the replacement of nitrogen. The mixture was refluxed at 65° C. for 12 hours. At the end of the reaction, acetone was removed by distillation under reduced pressure, and then the residue was dissolved by adding an appropriate amount of water. The pH of the solution was adjusted to 5-6 by adding 10% dilute hydrochloric acid, and the solution was extracted by adding ethyl acetate (10 mL×3). The organic layer was combined and dried with anhydrous sodium sulfate, and the organic solvent was removed by distillation under reduced pressure. The residue was separated by column chromatography on silica gel with dichloromethane:ethyl acetate=10:1 as an eluent to successfully obtain 202.2 mg of sulfinpyrazone 1 as a white solid in 50% yield.

Example 8

The reaction flask was sequentially added with 2-chloroethyl phenyl sulfoxide 2 (189.0 mg, 1.0 mmol), 1,2-diphenyl-3,5-pyrazolidinedione 4 (378.2 mg, 1.5 minol), cesium carbonate (488.7 mg, 1.5 mmol), potassium iodide (166.0 mg, 1.0 mmol), and acetone (6 mL), wherein the three-necked flask was inserted with a condenser tube connected with a three-way valve with a balloon on one side and covered with a rubber stopper on the other side for the replacement of nitrogen. The mixture was refluxed at 65° C. for 12 hours. At the end of the reaction, acetone was removed by distillation under reduced pressure, and then the residue was dissolved by adding an appropriate amount of water. The pH of the solution was adjusted to 5-6 by adding 10% dilute hydrochloric acid, and the solution was extracted by adding ethyl acetate (10 mL×3). The organic layer was combined and dried with anhydrous sodium sulfate, and the organic solvent was removed by distillation under reduced pressure. The residue was separated by column chromatography on silica gel with dichloromethane:ethyl acetate=10:1 as an eluent to successfully obtain 194.2 mg of sulfinpyrazone 1 as a white solid in 48% yield.

Example 9

The reaction flask was sequentially added with 2-chloroethyl phenyl sulfoxide 2 (189.0 mg, 1.0 mmol), 1,2-diphenyl-3,5-pyrazolidinedione 4 (378.2 mg, 1.5 mmol), cesium carbonate (488.7 mg, 1.5 mmol), sodium iodide (149.9 mg, 1.0 mmol), and acetonitrile (6 mL), wherein the three-necked flask was inserted with a condenser tube connected with a three-way valve with a balloon on one side and covered with a rubber stopper on the other side for the replacement of nitrogen. The mixture was refluxed at 65° C. for 12 hours. At the end of the reaction, acetone was removed by distillation under reduced pressure, and then the residue was dissolved by adding an appropriate amount of water. The pH of the solution was adjusted to 5-6 by adding 10% dilute hydrochloric acid, and the solution was extracted by adding ethyl acetate (10 mL×3). The organic layer was combined and dried with anhydrous sodium sulfate, and the organic solvent was removed by distillation under reduced pressure. The residue was separated by column chromatography on silica gel with dichloromethane:ethyl acetate=10:1 as an eluent to successfully obtain 125.4 mg of sulfinpyrazone 1 as a white solid in 48% yield.

It can be seen from the above that in the technical solution of the present disclosure, Examples 1 to 4 are the preparation of 2-chloroethyl phenyl sulfoxide in step 1, and Examples 5 to 9 are the preparation of sulfinpyrazone from 2-chloroethyl phenyl sulfoxide in step 1 in step 2. Compared with the prior art, introduction of a green and environmentally friendly electrochemical method into the synthesis steps not only greatly shortens the reaction steps, but also increases the overall yield; the use of strong bases and hydrogen peroxide as an oxidant is avoided, the atomic economy is improved and the environmental pollution is reduced; and the problem of easy over-oxidation of chloroethyl sulfide to chloroethyl sulfone under the hydrogen peroxide system is overcome fundamentally, and the selectivity of the reaction is improved. The preparation route according to the present disclosure has short steps, the yield of step 1) can reach up to 83%, and the yield of step 2) can reach up to 58% (see Example 5).

The above description is only a preferred embodiment according to the present disclosure, not thereby limiting the patent scope according to the present disclosure, and all equivalent transformations made by the present disclosure are within the scope of patent protection of the present invention. 

What is claimed is:
 1. A method for the preparation of sulfinpyrazone, wherein it has the following synthetic routes:

wherein electrolyte represents an electrolyte, current represents a current, temperature represents a temperature, salt represents a salt, base represents a base, additive represents an additive, and solvent represents a solvent.
 2. The method for the preparation of sulfinpyrazone according to claim 1, wherein it specifically comprises the following steps of: (1) dissolving thiophenol as shown in formula 3 and electrolyte in a mixed solution of 1,2-dichloroethane and water and reacting by passing the current for 1 to 48 hours to obtain 2-chloroethyl phenyl sulfoxide as shown in formula 2; and (2) mixing and dissolving 2-chloroethyl phenyl sulfoxide as shown in formula 2, 1,2-diphenyl-3,5-pyrazolidinedione as shown in formula 4, the base and the additive in the solvent, and reacting by heating under nitrogen atmosphere for 1 to 48 hours, and after completing the reaction, subjecting the reaction mixture to a column chromatography to obtain sulfinpyrazone as shown in formula
 1. 3. The method for the preparation of sulfinpyrazone according to claim 1, wherein the conditions of the electrodes in step (1) are as follows: the anode is selected from one of graphite felt, platinum, and nickel electrodes, the cathode is selected from graphite felt, platinum, nickel, and carbon sheet electrodes, and the electrode specifications are both 1 cm×1 cm.
 4. The method for the preparation of sulfinpyrazone according to claim 2, wherein the conditions of the electrodes in step (1) are as follows: the anode is selected from one of graphite felt, platinum, and nickel electrodes, the cathode is selected from graphite felt, platinum, nickel, and carbon sheet electrodes, and the electrode specifications are both 1 cm×1 cm.
 5. The method for the preparation of sulfinpyrazone according to claim 2, wherein the electrolyte in step (1) is any one of tetrabutylammonium bromide, tetrabutylammonium tetrafluoroborate, tetra-n-octylammonium bromide, tetrabutylarnmonium hexafluorophosphate, lithium perchlorate, ammonium perchlorate, and tetrabutylammonium iodide, and the amount of electrolyte is 0.5-2 times that of thiophenol.
 6. The method for the preparation of sulfinpyrazone according to claim 2, wherein the water in step (1) is any one of distilled water and deionized water, and the amount thereof is 0.5-10 times that of thiophenol.
 7. The method for the preparation of sulfinpyrazone according to claim 2, wherein the current in step (1) is 4-30 mA.
 8. The method for the preparation of sulfinpyrazone according to claim 2, wherein the temperature in step (1) is 30-70° C.; and the amount of 1,2-dichloroethane in step (1) by volume is 5-30 times that of compound
 3. 9. The method for the preparation of sulfinpyrazone according to claim 1, wherein the solvent in step (2) is selected from any one or more of acetone, acetonitrile, and n-hexane.
 10. The method for the preparation of sulfinpyrazone according to claim 2, wherein the solvent in step (2) is selected from any one or more of acetone, acetonitrile, and n-hexane.
 11. The method for the preparation of sulfinpyrazone according to claim 2, wherein the base in step (2) is selected from any one of cesium carbonate, sodium hydroxide, potassium hydroxide, sodium ethoxide, potassium ethoxide, triethylamine, and diisopropylethylamine; the additive is selected from any one of sodium iodide, potassium iodide, lithium iodide, and ammonium iodide; and the reaction temperature in step (2) is 50-70° C.
 12. The method for the preparation of sulfinpyrazone according to claim 2, wherein the amount of the compound 1,2-diphenyl-3,5-pyrazolidinedione in step (2) is 1.0-4.0 times that of 2-chloroethyl phenyl sulfoxide; the amount of base is 1.0-4.0 times that of 2-chloroethyl phenyl sulfoxide; the amount of additive is 1-5 times that of 2-chloroethyl-1 phenyl sulfoxide; and the amount of solvent is 5-10 times that of 2-chloroethyl phenyl sulfoxide. 